Charge Reconstruction with a Magnetised Muon Range Detector in TITUS

Transcription

1 Charge Reconstruction with a Magnetised Muon Range Detector in TITUS Mark A. Rayner Université de Genève 5 th open Hyper-Kamiokande meeting, Vancouver 19 th July 2014, Near Detector pre-meeting

2 Motivation Significant wrong-sign component in anti-neutrino mode σ(υ) / σ(υ) courtesy of Raj Shah s Valor analysis The anti-neutrino crosssection is the biggest unconstrained model systematic 2

3 υ n l p υ p l n detect with Gd ε Q 88% Exciting, but somewhat untested 3

4 18% of muons escape the tank red: mu- leave tank blue: mu+ leave tank green: mu- stop in tank purple: mu+ stop in tank R 2 (mm 2 ) z (mm) N.B. The tank size could be re-optimized with the MRD in mind courtesy of Matthew Malek 4

5 MRD design considerations iron scintillator Vary side coverage Do we stop a useful fraction of muons given the cost? μ μ μ Magnetize charge and momentum 1.5 Tesla (near saturation in cheap steel) 450cm (150cm of which Fe) α μ neutrino beam μ μ 20 Fe+scintillator modules 150cm α μ Grade downstream Fe thickness? 2.5 cm 5cm, ~1 euro / kg Constant scintillator thickness 2.5 cm ( 0.75cm?) 20 CHF / SiPM + 20 CHF / electronics channel 5

6 Muons tracks in the TITUS MRD A simulation with 150cm end Fe and 75% side coverage of 50cm of Fe range-out and stop in the MRD penetrate through the MRD miss the MRD not to scale υ υ υ 6

7 And from two more projections 7

8 ~70% of muons are stopped In 150cm of Fe muons lose about 2 GeV Aside Momentum for the stopping sample: For e.g. 2.5 cm iron planes, sample energy at 35 MeV 8

9 Optimizing efficiency for stopping muons, and cost 1.e6 Solid lines for equal side thickness Dashed lines for 1/3 side thickness 9

10 x = ± R Magnetization of the MRD B not to scale field density here is 3/2 87% of that here y 0.5 m 30 R=5.5m x t 10

11 Multiple Scattering in the iron is the biggest obstacle to charge reconstruction θ X 0 = cm in Fe X 0 = cm in polyethylene (X 0 / X 0 ) ½ = 1.9% ψ 11

12 To start with, a probabilistic, back of a (fairly big) envelope calculation μ+ μ inefficiency 1 p θ MS 0 θ B angle of deflection 12

13 TITUS MRD charge recon. efficiency vs. muon energy PRELIMINARY 13

14 TITUS MRD charge recon. efficiency vs. neutrino energy PRELIMINARY 14

15 but of course E ν < 2 GeV is of particular interest PRELIMINARY mean = 81% Here we expect ~80% efficiency Let s think more carefully about this region 15

16 What is the E μ composition of the side MRD? 0.6 GeV 0.5 GeV 0.4 GeV 0.3 GeV 0.2 GeV ¾ of events with muons which leave the tank 16

17 What is the E μ composition of the end MRD? 0.6 GeV 0.5 GeV 0.4 GeV 0.3 GeV 0.2 GeV More forward muons have slightly higher energies 17

18 E μ = 0.6 GeV 56% of END muons 32% of SIDE muons 18

19 E μ = 0.6 GeV 56% of END muons 32% of SIDE muons at low angles, even when there is significant Multiple scattering, curvature yields the charge 19

20 E μ = 0.6 GeV 56% of END muons 32% of SIDE muons at low angles, even when there is significant Multiple scattering, curvature yields the charge at high angles, curvature is more difficult to distinguish, but range is a powerful discriminator 20

21 E μ = 0.5 GeV 20% of END muons 21% of SIDE muons 21

22 E μ = 0.5 GeV 20% of END muons 21% of SIDE muons a trickier case, but a clear choice given we know the initial angle from the Cherenkov ring range is still essential at high angles 22

23 E μ = 0.4 GeV 14% of END muons 24% of SIDE muons Landau- Vavilov?? 23

24 E μ = 0.4 GeV 14% of END muons 24% of SIDE muons Landau- Vavilov?? knowledge of the initial angle is essential now 24

25 E μ = 0.3 GeV 7% of END muons 17% of SIDE muons Here I suspect we got a bit lucky! It s a probabilistic game, but still promising at 0.3 GeV 25

26 E μ = 0.2 GeV 2% of END muons 7% of SIDE muons only one measurement Totally dominated by position resolution and number of sampling points 26

27 E μ = 0.2 GeV 2% of END muons 7% of SIDE muons only one measurement A courageous idea? Could replacing the first two scintillator layers of the MRD with a drift chamber help us out? sub-mm resolution from the drift time Much better than 2.5 cm / 12 from the normal which slab? method Would also help with measuring the initial angle and matching tracks Needs to be demonstrated Totally dominated by position resolution and number of sampling points 27

28 Baby-MIND and TASD: H8 beamline in North Area (or possibly behind the LBNO-Demo) 1.5 Tesla 3 m 2.5 m 1.5 m Could also be a test of the TITUS MRD charge reconstruction Contact: Etam Noah, University of Geneva 28

29 The B2 experiment / WAGASCI Another possible Baby-MIND synergy Taichiro Koga 29

30 Summary 18% of muons escape the 22 m long, 11 m diameter TITUS tank 75% through the sides, 25% through the end With 150 cm of iron at the end, 50 cm of iron at the sides: 75% of muons which escape the tank are stopped 25% of muons which escape the tank penetrate through the MRD Preliminary studies show promising charge reconstruction in the oscillation region and impeccable resolution in the high energy tail (1.5 Tesla) Work in progress Find the effect on δ CP sensitivity Optimization of scintillator and irons layer thicknesses Answers to practical questions, such as PMT shielding The last lever: consider re-optimising the tank size and MRD size simultaneously 30

31 Backup slides 31

32 TITUS tank angle reconstruction? 1 sigma electron ring 1 sigma muon ring from the fitqun technical note 32

33 Taichiro Koga 33

34 The B2 experiment Taichiro Koga 34

35 Taichiro Koga 35

36 3 cm steel 1.5 cm scintillator 2 cm steel 1.5 cm scintillator 98.0% 98.5% p μ = 0.5 GeV/c E μ = 0.51 GeV Muon momentum (GeV/c) 3 cm steel 3.5 cm scintillator 2 cm steel 3.5 cm scintillator 97.5% 98.0% Proposal for SPS beam time for the baby MIND and TASD neutrino detector prototypes, R. Asfandiyarov et al. 36

37 range < 15 cm 37

38 Aside: Momentum for the penetrating sample Curvature in B-field signal Mean Multiple Scattering error Multiple Scattering 38

39 measure E μ = 2.5 GeV with resolution 0.5 GeV 20% 39

40 measure E μ = 2.5 GeV with resolution 0.5 GeV 20% measure E μ = 6.5 GeV with resolution 1 GeV 15% Very conservative estimates 40

41 Landau-Vavilov most probable energy loss in iron density = 7.87 g cm -2 K = MeV g -1 cm 2 ~ 1.13 MeV / cm (ultra-relativistic) Z/A = 26 / = <Z/A>ρ ratio (~energy loss / cm) = 1.4% MeV neglect density effect Mean excitation energy I = ev in iron all materials 41

42 42

43 Range of muons in iron iron Fiducial volume cut = 1 m with LAPPDs = 0.5 m 43

44 PDG Measurement of particle momenta in a uniform magnetic field 44

45 45

46 Curvature in the magnetic field θ The uniform magnetic field B = 1.5T is in the z direction The particle moves along a curve of length s in the (x,y) plane dp /dt = B q ds/dt ψ Δp = B q Δs Take uniform steps of Δs = 1 cm Δp = 4.5 MeV/c (for every cm) And hence the angle curved, depending on E at the time ΔE using most probable Landau-Vavilov value (Bethe overestimates due to long tails) Charge identification for the muon if θ > Multiple Scattering 46

47 Muon path length in the iron of the MRD six 3cm Fe planes 47